The present invention relates to an ink jet printing apparatus. In such an apparatus, ink is supplied into an ink jet head and subjected to pressure oscillation by a vibrator. This pressure oscillation causes the ink to be ejected from the head and separate into droplets. Where it is desired to print a drop on a sheet of paper, an electrostatic charge is applied to the droplets. The charged droplets are electrostatically deflected by deflection electrodes and hit the paper to print the dot. Where it is not desired to print a dot, the droplets are not charged and are therefore not deflected by the deflection electrodes and hit a gutter instead of the paper.
In many applications, it is desirable to be able to vary the size of the characters or other image being printed by the apparatus. This has been done in the prior art by providing a character generator which stores character patterns of the various sizes. However, this expedient is not entirely satisfactory due to the requirement of a large character generator for storing the multiple patterns and the control circuitry for changing between the various sizes.